Digital broadcast service includes the real-time broadcast service intended to be viewed in real time as ordinary television broadcast service, and the download broadcast service intended to be stored in a receiver once and then to be reproduced and viewed. The download broadcast service cannot be viewed in real time, but it can be operated as a service capable of storing programs with a high transmission rate for a shorter time than being usually viewed. Furthermore, broadcast service can be carried out by switching the two types of broadcast service in terms of time. For example, a mixed operation is possible in which the real-time broadcast service is carried out during the daytime and the download broadcast service of programs whose audience ratings are high in that day is carried out at midnight.
FIG. 7 shows a configuration of a digital broadcast system including a digital broadcast transmitter that carries out the mixed operation and a conventional digital broadcast receiver corresponding to the mixed operation.
In digital broadcast transmitter 100, for the real-time broadcast service, MPEG-2 transport stream multiplexing unit 104 multiplexes video/audio data output from video/audio encoding unit 102 and real-time broadcast program information output from real-time broadcast program information generating unit 103 in the MPEG-2 SYSTEM mode. MPEG-2 transport stream multiplexing unit 104 outputs an MPEG-2 transport stream to switching unit 108.
On the other hand, for the download broadcast service, download broadcast signal multiplexing unit 107 multiplexes video/audio data for the download broadcast service, which is output from content storage unit 105, and download broadcast content information output from download broadcast content information generating unit 106 in a download broadcast signal multiplexing mode. Download broadcast signal multiplexing unit 107 outputs a download broadcast signal to switching unit 108. As the download broadcast signal multiplexing mode at this time, a multiplexing mode by a variable-length packet is used with the consideration of the transmission efficiency. For example, in the Advanced BS Digital Broadcast in Japan, as the download broadcast signal multiplexing mode, the TLV (Type Length Value) multiplexing mode is used, and the download broadcast signal is referred to as a TLV stream.
Switching unit 108 selects the MPEG-2 transport stream during the real-time broadcast service. Switching unit 108 selects the download broadcast signal during the download broadcast service. Digital broadcast transmitting unit 101 modulates the selected signal into a digital broadcast signal and outputs the modulated signal to transmission line 300.
When broadcast service is carried out by switching two types of broadcast service in terms of time, the real-time broadcast program information is broadcasted only during the real-time broadcast service, and the download broadcast content information is broadcasted only during the download broadcast service. Therefore, digital broadcast receiver 200 sometimes cannot obtain the real-time broadcast program information or the download broadcast content information in specific timing.
In order to solve this problem, the download broadcast content information output from download broadcast content information generating unit 106 is also output to communication network 400 through communication unit 109. Thus, even during the real-time broadcast service, digital broadcast receiver 200 can obtain the download broadcast content information.
On the other hand, digital broadcast receiver 200 receives the digital broadcast signal flowing in transmission line 300. Digital broadcast receiving unit 201 demodulates the digital broadcast signal. Then, digital broadcast receiving unit 201 outputs the MPEG2 transport stream to MPEG-2 transport stream de-multiplexing unit 202 during real-time broadcast. Furthermore, digital broadcast receiving unit 201 outputs the download broadcast signal to download broadcast signal de-multiplexing unit 204 during download broadcast.
For the real-time broadcast service, MPEG-2 transport stream de-multiplexing unit 202 separates video/audio data and real-time broadcast program information from the MPEG-2 transport stream. The real-time broadcast program information is stored in real-time broadcast program information storage unit 203. The video/audio data pass through video/audio switching unit 207, decoded in video/audio processing unit 211, and are output from video/audio output unit 212, so that a viewer views the real-time broadcast service.
For the download broadcast service, download broadcast signal de-multiplexing unit 204 separates video/audio data and download broadcast content information from the download broadcast signal. Furthermore, during the real-time broadcast service, communication unit 213 obtains the download broadcast content information flowing in communication network 400. The download broadcast content information obtained from transmission line 300 or communication network 400 is stored in download broadcast content information storage unit 206. The video/audio data are stored in content storage unit 205 only when they are programs instructed to be stored by a viewer. The stored video/audio data are output from content storage unit 205 when a viewer instructs reproduction. Then, the video/audio data pass through video/audio switching unit 207, are decoded in video/audio processing unit 211, and are output from video/audio output unit 212. Thus, a viewer can view the download broadcast service.
When a viewer instructs an electronic program guide (hereinafter, abbreviated as “EPG”) of the real-time broadcast service to be displayed, real-time broadcast EPG generating unit 208 takes out the real-time broadcast program information from real-time broadcast program information storage unit 203, forms EPG display data, and outputs the formed data. The EPG display data pass through EPG/ECG (Electronic Content Guide) switching unit 210, are synthesized with video data in video/audio processing unit 211, and output from video/audio output unit 212.
Furthermore, when a viewer instructs an electronic content guide (hereinafter, abbreviated as “ECG”) of the download broadcast service to be displayed, download broadcast ECG generating unit 209 takes out the download broadcast content information from download broadcast content information storage unit 206, forms ECG display data and outputs the formed data. The ECG display data pass through EPG/ECG switching unit 210, are synthesized with video data in video/audio processing unit 211, and are output from video/audio output unit 212.
The real-time broadcast service and the download broadcast service use utterly different multiplexing modes. For the download broadcast content information, a mode different from EIT (Event Information Table) and the like which is usually used in the real-time broadcast service is used. Therefore, in a conventional digital broadcast system, these two broadcast services are distinguished from each other as individual services. More specifically, the digital broadcast transmitter broadcasts only real-time broadcast program information in the real-time broadcast service, and broadcasts only download broadcast content information in the download broadcast service. In the digital broadcast receiver, the EPG for the real-time broadcast service is displayed on a screen by using only the real-time broadcast program information, and the ECG for the download broadcast service is displayed on a screen by using only the download broadcast content information. The EPG and the ECG are displayed on different screens.
The download broadcast content information and the real-time broadcast program information are described in detail. FIG. 8 shows examples of conventional download broadcast content information and real-time broadcast program information, FIG. 9 shows an example of EPG display data in a conventional digital broadcast system, and FIG. 10 shows an example of ECG display data in a conventional digital broadcast system.
The download broadcast service uses download broadcast content information that is the same as content information in a communication download service so that the download broadcast service is compatible with the communication download service. Therefore, the download broadcast content information includes a sender address, content ID, and a content name of each content as shown in the left column of FIG. 8. Furthermore, a delivery date and time, and duration are also included as information that is not included in the content information of the communication download service. Furthermore, as shown in content information 2 in FIG. 8, a plurality of delivery dates and times, and duration including those of rebroadcast may be described in one piece of the content information.
Furthermore, as information specific to the download broadcast service, address map information indicating a combination of a channel number and a sender address is also used. Furthermore, the real-time broadcast program information includes program information indicating a channel number, program ID, starting date and time, duration, and a program name of each program as shown in the right column of FIG. 8. In this way, since the information included in the download broadcast content information is different from that included in the real-time broadcast program information, it was necessary to use them separately. From the above description, since an EPG screen uses only the real-time broadcast program information, the screen is displayed in a state in which a time zone of the download broadcast service is blank as shown in FIG. 9. Furthermore, since an ECG screen uses only the download broadcast content information, the screen is displayed in a state in which a time zone of the real-time broadcast service is blank as shown in FIG. 10.
One example of a conventional digital broadcast system is a digital broadcast receiver capable of converting a display form of an EPG according to the conditions provided by a viewer (see, for example, Patent Literature 1).
Another example is a digital broadcast receiver which obtains predetermined program information by using another communication means when it is determined that obtaining of the predetermined program information has not been completed (see, for example, Patent Literature 2).
A still another example shows that program information to which information indicating whether a program requires a storage function at a receiver is added is broadcasted from a digital broadcast transmitter, in which the program information is displayed in such a manner that is distinguished from the other information on an EPG of the digital receiver. (See, for example, Patent Literature 3).
However, in the above-mentioned conventional digital broadcast system, when the real-time broadcast service and the download broadcast service are switched from each other in terms of time and broadcasted, the real-time broadcast program information includes only program information of the real-time broadcast service. Therefore, since no program information for the download broadcast service is included, a time zone of the download broadcast is blank on the EPG screen.
In the digital broadcast system described in Patent Literature 1, a digital broadcast receiver is provided with means for converting display forms of the EPG according to the conditions provided by a viewer. However, program information to be used at that time is only the program information of the real-time broadcast service. Therefore, similarly, a time zone of the download broadcast service in which program information does not originally included is blank on the EPG screen.
In the digital broadcast system described in Patent Literature 2, a digital broadcast receiver is provided with means for obtaining real-time broadcast program information, which has not been obtained, by using another communication means. However, since program information to be used at that time is only program information of the real-time broadcast service, a time zone of the download broadcast service in which program information does not originally included is blank on the EPG screen, which is similar to the above.
The digital broadcast system described in Patent Literature 3 provides means for displaying an EPG with information for distinguishing information added in program information when the real-time broadcast service and the download broadcast service are mixed by using the same multiplexing mode. However, this assumes that two pieces of broadcast program information are multiplexed in the same multiplexing mode. Consequently, when the download broadcast service whose multiplexing mode is different is mixed, a time zone of the download broadcast service in which no program information is included is similarly blank on the EPG screen.
Therefore, by only watching the EPG screen, a viewer cannot discriminate whether the time zone in which the EPG screen is blank signifies suspension of broadcast or during download broadcast.